1. Field of the Invention
The present invention relates to a flat panel display, more particularly, to an organic electroluminescent display device capable of improving luminance non-uniformity and extending life time by removing a height difference between an anode electrode and a pixel define layer so that a good organic thin film layer is formed, and a fabrication method of the organic electroluminescent display device.
2. Description of the Related Art
FIG. 1 illustrates a cross sectional view of a conventional organic electroluminescent display device. Referring to FIG. 1, anode electrodes 21 are formed on a substrate 20 spaced apart from each other in a certain distance per each pixel, such as R, G and B unit pixels. A pixel define layer 23 is formed on the substrate 20 so that a portion of the anode electrode 21 is exposed to form an opening 22. The pixel define layer 23 has an organic insulation film, which defines neighboring anode electrodes 21 per each pixel. An R, G or B emitting layer 25 is formed on the opening 22 of the anode electrode 21. A cathode electrode 27 is formed on the substrate 20 above the layer 25. Although it is not illustrated on drawing, the emitting layer 25 has at least one layer selected from a hole injection layer, a hole transport layer, a hole barrier layer, an electron injection layer and an electron transport layer.
Important features of the organic electroluminescent display device are a flatness of a conductive material used in the anode electrode 21 and a structure of the pixel define layer 23 having the organic insulation film for determining size of the opening 22 in the anode electrode 21. Conventionally, the anode electrode 21 is formed by patterning a deposited anode electrode material after depositing an anode electrode material on the substrate 20. The pixel define layer 23 is subsequently formed by patterning a deposited organic insulation film to expose a portion of the anode electrode 21 after depositing an organic insulation film on the substrate 20. Therefore, the pixel define layer 23 is formed in such a manner that the pixel define layer 23 has a higher step difference than the anode electrode 21 as shown in FIG. 1.
As described above, the conventional organic electroluminescent display device has problems in that a polymer remains since the pixel define layer 23 is formed by patterning the organic insulation film using a photosensitive photoresist. Furthermore, the conventional organic electroluminescent display device has problems in that a luminance becomes non-uniform and the life time deteriorates since the emitting layer 25 and the cathode electrode 27 are incompletely formed during the process of successively forming the emitting layer 25 and the cathode electrode 27 due to an angle of a part of the pixel define layer 23 having a step difference from the anode electrode 21. Also, the organic thin film layer deteriorates by outgassing generated from the photoresist. Moreover, the conventional organic electroluminescent display device has had problems due to contact defects generated between the anode electrode 21 and the organic emitting layer 25 since an organic material is not properly transferred at the part of the pixel define layer 23 having the step difference from the anode electrode 21 when the organic emitting layer is formed using a laser induced thermal imaging method.